Boris Katan flights 2016 -> Clusters + 3D Printing Fun <-

For 2016 I will continue to post all my projects and flights in one annual thread as in previous years.
This makes is easier for me to post, and easier to follow for anyone who subscribes.
Also avoids having threads for some projects and not others.

In November 2015 acquired and assembled a Rostock MAX 3D printer kit. Chosen because it has a large build area – 280mm diameter x 350mm tall - and a reputation for good quality prints.

Kit took about 30 hours to build, following 280 pages of instructions for hardware assembly, software setup and calibration. 500+ pieces in all. Followed all instructions precisely, to minimize problems and maximize printing when done. Building familiarity with 3D printing and CAD software, and adding capabilities to the base printer have been my winter project this year. Taking hundreds of hours and printing many dozens of test and usable parts so far.

Goals are to learn about and use a cool new technology and to 3D print a variety of rocket parts.
Only thing better than one great hobby is using one to complement another!

While filament deposition 3D printers can work with a variety of materials, my primary interest is working with ABS because:
1) it is more heat resistant than many other 3D printable plastics
2) it is physically resilient and shock resistant
3) it can be welded and/or surface finished with acetone
4) it sands and cuts in a manner fairly similar to wood

However, ABS shrinks as the temperature changes after the hot melt process used for 3D printing. So larger ABS parts require a heated print chamber to greatly slow down the cooling/temperature transition process. Final cooldown after the print is complete prevents large ABS parts from warping. As the printer kit does not include a heated chamber, had to add one.

Hardest part was shaping the top and bottom as they had to conform to the printer.
Used DAP Contact Cement to adhere tinfoil to inner surfaces of chamber during assembly.
Elmer's wood glue attached 1"x2" corner rails to a wall.
Then screwed wall assemblies together.

Designed so each wall, top, bottom and door can be removed with screws if necessary.

Used a popcicle stick to smooth out slight wrinkles in Tinfoil and aluminum tape as needed.
First screwed in top and bottom sections.
Then screwed on sides and back.
After each step, applied aluminum tape liberally to seal corners and make sure all internal surfaces were heat reflective.

For the enclosure door, used 3 overlapping layers of 1/4" marine plywood.
Middle layer was not as wide as front and back layers, creating a pocket to hold the Lexan polycarbonate window.

As the Lexan was thin, used two layers with a thin air gap. This fit well in the 1/4" pocket created by the plywood. Elmer's wood glue bonded the plywood.

Covered door with aluminum tape. 3 small hinges and a magnetic door catch secure the door.

Installed a 300W rated ceramic lamp fixture with a 250W (120V AC) heat lamp in the upper left side of the enclosure. Temperature limited by an Inkbird ITC-2000 controller set to shut off at 70C. Most of the time the chamber sits at a natural temperature equilibrium at 60-70C, once in a while hitting 70C and shutting off the heat lamp for a minute or two.

This has been effective in preventing any warping in the larger ABS prints completed so far.

1) Added 4 legs to the enclosure, giving the modified printer a broader and much more stable base.
The enclosure is rigid enough that there is no structural flexing at all. Particularly beneficial when the door is open, as that shifts the center of balance significantly.

2) Installed a relay to automatically power on and off the chamber heat lamp at the same time as the heated filament extruder head.

3) Replaced printer’s 12V power supply with an Antec 450 watt PC power supply for more coinsistent power delivery. Used a large 50A rated dryer plug as a connection point between printer and PS. Did not want to use a standard 120 VAC outlet as the consequences of accidentally connecting 120V power to the 12V system is much nastier than I would ever want to contemplate. Done so I can carry the printer more easily on those rare occasions when that comes up.

Completed just before I brought the printer to my work for show and tell. I teach a Computer and Networking Tech program at a trade school. The 3D printer generated a lot of excitement and interest.

1) a 100mm diameter saucer with a single vertically mounted 18mm motor mount and

2) a 200mm spinning saucer with 2x 18mm motor mounts, a mini version of my other spinning saucers.

These both flew at the CMASS Winter Follies launch in Acton, MA on 1/17/2016.

The 100mm conventional saucer flew on a B6 and a C6.

I set up the 200mm saucer 5 times for flight, first with 2x B6 and then the following flights were set up with 2x C6 power. Due to a combination of factors only one of these flights successfully fired both motors, the other 4 attempts all fired just one motor. I believe there was a stacking of factors, cold temperature slowed the firing of both igniters and motors, high relative humidity, the motors were positioned very close to the clothespins I was using to hold the rocket up the rod and kept tangling with the igniters as the rocket spun.
These four cluster ignition failures were twice as many as I had all of last year.

Also flew an Applewhite 12inch Classic Saucer twice on AT G53 Smokey motors.

Next modded printer with the E3D Volcano print head which uses larger extrusion nozzles.
“Standard” extrusion nozzles are 0.4 or 0.5mm. Volcano nozzles are available in 0.6, 0.8, 1.0 and 1.2mm sizes. Used a PC Molex connector to facilitate swapping print head.

Volcano Pros: faster and stronger prints and a more reliable printing process

Con: rougher/cruder surface finish

Printed several 150mm red conventional saucers with a central 24mm motor mount testing different nozzles and settings. Decided that I liked the 0.6mm nozzle size best for its balanced compromise of features.

Filament deposition 3D printing builds prints up a layer at a time, so each print starts from a flat surface and shape overhangs must be managed carefully. Either the part only spreads gradually from its base, or some kind of support is required.
Pic 1 and 2: If support uses the same material as the desired part, then a significant amount of cutting, and sanding is likely to be required. Part surface quality in these trimmed areas suffers.

There is also a grain to filament deposition printing. Fine strands of heated plastic are laid out in the X and Y “horizontal” dimensions, so these are strongest. Filaments are built up in layers in the Z “height” dimension, so anything less than excellent layer adhesion between every single layer results in less stiffness and ultimate strength in this dimension.

For both of these reasons, planning the orientation of the part during the print process is critical.

Another technique to handle support for 3D printing overhanging part shapes is to use a second type of plastic that is thermally and mechanically similar, but chemically incompatible for support. Then it is possible to cleanly separate the part from the support by pulling them apart. With ABS printing, it is possible to use HIPS (high-density polystyrene) for support material. They melt at similar temperatures, but with different chemistry, are not prone to bond to each other.

So the next modification was a big one - convert the printer to be able to handle two filament materials at the same time. The stock Rostock MAX, like many other printers, was designed to handle one filament at a time.

Pic 3: Two Bondtech QR filament drivers were added to the printer. The second filament driver and the new heated print head required additional wiring and modifying firmware settings to the Rambo (Arduino processor) logic board in the printer. Yellow filament is ABS and white is HIPS.

Pic 4: A E3D Cyclops heated print head was installed. This is a new design that had two filament inputs, but extrudes both materials through one nozzle. Alternative design options not chosen would have had two filament inputs feeding two nozzles.

Cyclops pros: easier alignment with one extrusion nozzle, less risk of second nozzle bumping into part, less dripping of hot plastic from second nozzle not in use (all frequent problems)

Cons: Still a fairly experimental design so tuning process is to be expected, cross contamination of incompatible plastics will have to be overcome

As the Cyclops is only currently available with a 0.4mm nozzle, I purchased several 0.6mm drill bits and extra nozzles. On the second attempt, with oil lubrication, was successful in drilling a nozzle to 0.6mm. This is what I print with now.

Designed a mount/cover for the 808 #16 video camera. With 720 30p capability and a moderate price, my preferred onboard video camera for rocketry.
The angles necessary for aerodynamic shape of the mount and conforming to rocket body required support for 3D printing.

This was my process calibration/test part for refining ABS + HIPS printing with the Cyclops.
Pic 1: It took about 20 prints to get the process dialed in.
Pic 2 and 3: Failure mode for earlier prints was weak layer adhesion between ABS layers due to cross contamination from HIPS.

Pic 4 and 5: Primary elements of successful process were very large retraction of filaments when switching filament types, as well as a very large sacrificial “wipe tower” used during filament transitions. While the basic approach is intuitive, getting these and many other settings dialed in were a process.

Many designs do not require support, and these can be efficiently printed all in one material. Having done a few saucers, wanted to do a more conventional rocket shape that was also 100% 3D printed.

Worked up a stretch V2 design that was 2 inches diameter, with a 12 inch nose cone and 12 inch body. Inside top of NC has tubular ribbed area to receive and retain ¼ oz nose weight and epoxy. Both major rocket parts were printed with rocket separation point facing down, to avoid overhangs. Also printed a plug for the bottom of the NC and bonded to NC using acetone.

Did run into print quality issues with the tip of the NC so tweaked settings on a bunch of test NC tips until these were dialed in and got a nice final product.

2 inch diameter x 24 inches tall, designed to fly on a D12-5 with a flight weight of 9oz. A fun little flyer that is a prototype larger things to come…

Future projects on a larger scale will be printed in sections and “welded” together with acetone. Some will include conventional rocket body tubes with 3D printed nose cones and tail/fin sections

Rained heavily for most of the two hour drive to the field, letting up just minutes before arrival. Cloudy with no wind in the morning, becoming sunny and gorgeous in the afternoon.

First flight was the Mellow Yellow on a D12-5. Nice straight liftoff, shock cord separated on deployment, but the ABS was tail section was undamaged from its fall.

Then the Soyuz went up on a central CTI G68 White + 16x D11-P engines in the boosters. Went up nicely on a column of fire and smoke, firing all motors and arcing over at 604ft.

Recovered in two parts on 3ft and 4ft chutes. One of the tiny fin tips broke off, easily fixed. The escape tower will need the sacrificial tube section (1/2in launch lug) replaced, but that was expected.

Prepping for the Joint CMASS / MMMSC launch at the large, beautiful field in Berwick, ME.

Midnight Express:
> Built up three strips of 6oz FG followed by two layers of 1oz at the fin root to body tube joint on two fins
> Started with 2in wide strips and each successive layer was 1/8in wider
> Pigmented most of the epoxy resin black to better match CF fins

> Also 3D printed a new cover for the 5.6in diameter chute compartment inside the NC
> This increased space for the chutes when flying K power and single deploy

I sent the Midnight Express (3.4x Big Daddy) up on the always delightful CTI 54mm 4grain K740 C-Star.

The liftoff was bright and loud and lovely.
The 36lb, 10in x 68in rocket hit apogee at 1464ft

The recovery was less delightful...
Ejection charge separated the rocket, could even make out the puffs for the 2 redundant ejection charges (one alt and one motor fired).
Unfortunately the harness tangled and never gave the chutes the pull they needed to exit their compartment.

The good news is that the rocket landed on soft loose dirt. The NC with altimeters was undamaged, the fins were also still solid. Only the upper body tube will need to be replaced. Still have the tube sections needed to complete the repair as spare pieces left from the original build for my L3 in 2012.

This flight had all the harness outside the chute compartment. Thought I had folded and packed it so that it would deploy, but that did not occur...
Next time the harness will be partly inside the chute compartment and partly outside.